The basic processes for this synthesis are, in general, already known.
In U.S. Pat. No. 3,950,438 (the disclosure thereof is incorporated herein by reference), such a process is described wherein delta keto esters are converted in one step into the corresponding resorcinol; (however, variable amounts of the corresponding dihydro resorcinol and also some phenol are nonetheless formed as by-product therein). Furthermore, U.S. Pat. No. 3,932,511 (the disclosure thereof is incorporated herein by reference) has described a process for the cyclization of delta keto esters to form the corresponding dihydroresorcinol.
The overall yields obtained in said U.S. Pat. No. 3,950,438 are good, but not as high as is to be desired. While high yields for the production of the dihydroresorcinols are provided in U.S. Pat. No. 3,932,511, that product must still be dehydrogenated to obtain the desired resorcinol.
It is also known that such a dehydrogenation of dihydroresorcinols can be effected by conducting that reaction in a solvent by the procedure described in the published Netherlands patent application No. 75 09211. In this operation a rather high yield can be obtained, provided that di-, tri- or tetraethyl-glycol dialkylethers is used as solvent. However, these solvents are rather expensive, and their use as reaction media thus impose a substantial price for obtaining a good yield.